1. Field of the Invention
This invention relates to a grinding apparatus and more particularly a grinding apparatus for reforming a surface of a commutator of an electric motor, which is adapted to be mounted for use at an opening of a casing of the motor for changing carbon brushes.
As a result of sliding contact of the commutator with carbon brushes over a long period of time, the surface of the commutator can be adversely affected by oxidation, spark discharge and the like, so that the surface is more or less damaged whereby its commutation is remarkably diminished and therefore it needs to be reformed to a smooth surface by grinding.
2. Description of the Prior Art
Various kinds of grinding apparatus have been suggested to date. For example, a main grinding spindle is supported by arms on supporting struts having bottom ends bolted to a coupling for a driving shaft of a motor, or a main spindle is supported on supporting struts fixed by a magnetic substance to one side of a casing of the motor. In this case, the damaged surface of the commutator is ground by a grinding stone held by an arm at the front end of the main grinding spindle while the commutator is rotating. These devices, however, have the disadvantages that the struts, arms and main spindle constitute a very long support which may give rise to a wandering of the apparatus and unavoidable chattering when grinding, and there is a tendency of the apparatus to change its initial position during operation, which makes it impossible to grind the surface of a commutator with a high accuracy.